Narcotic analgesics (morphine and many of its homologous) when administered in medicinal doses, relieve pain and produce sleep. Since, these drugs relieve pain and produce sleep, therefore are chiefly used for the relief of postoperative pain, cardian pain and pains of terminal cancer, and in child birth.

Drugs that bind to the receptor site and inhibit its natural function are called antagonist, drugs e.g., cimetidine is an antagonist drug because it binds to the receptor site in stomach otherwise histamine will bind to the receptor site and induce the secretion of HCl in stomach.

Thus, this antacid blocks the receptor site and hence, the secretion of HCl is reduced thereby reducing/removing hyperacidity.

An antimicrobes tend to destroy/prevent development or inhibit the pathogenic action of microbes such as bacteria, fungi, virus or other parasites selectively. Thus, antimicrobial are drugs which cure diseases caused by microorganisms.

Soaps are sodium or potassium salts of long chain fatty acids such as stearic acid, oleic acid and palmitic acid. Soaps containing sodium salts are formed by heating fat (i.e., glyceryl ester of fatty acid) with aqueous sodium hydroxide Ans.

This reaction is known as saponification. In this reaction, esters of fatty acids are hydrolysed and the soap obtained remains in colloidal form. It is precipitated from the solution by adding NaCl . The solution left after removing the soap contains glycerol as side product.

Bathing soaps are potassium salts of long chain fatty acids. They are usually soft and are also free from unused alkali. On the other hand, washing soaps are sodium salts of long chain fatty acids. They are usually hard and also contain some residual alkali.